Wednesday, October 28, 2009
CCTV Monitors or TVs
The signal from a cctv camera is classed as analogue, 1 volt peak to peak into 75 Ohms. A compatible display device must be used to view the images.
The simplest method of displaying the images from the camera is by connecting to the AV input or SCART input on a television set. Most modern TVs now have these type of inputs. The AV input is usually a RCA/Phono type of connector. A simple BNC to Phono converter is all that is required to connect cameras fitted with a BNC type of connector. Most of our camera kits are supplied with BNC and Phono connectors. Alternatively, a BNC to SCART connector can be purchased as an optional extra.
Switchers, multiplexers and digital recorders generally have BNC input connectors.
If you have an older type television that does not have an AV or SCART connector it is possible to convert the camera signal to the broadcast frequency and connect through the aerial input. A small device called an RF Modulator or Wide Band Modulator provides this function.
Alternatively, for more complex or dedicated cctv system a specialist cctv monitor can be used. The tubes or screen (referred to as the CRT)used in cctv monitors are of a much higher resolution than standard TVs. The resolution is measured in TV lines and on monochrome monitors this can be up to 1000TV lines. A good quality TV will be classed at 450 TV lines. These figures are measured at the centre of the tube and will be less at the edges.
Monitors are also designed for continuous running and will contain a high-reliability long-life power supply.
If you are fitting high definition cameras with over 500 TV Lines resolution then a suitable cctv monitor is needed.
LCD screens are now available for cctv applications. The advantages of LCD monitors are:
They are smaller and lighter than CRT monitors
Offer the possibility of 12 volt operation
Offer high resolution that is uniform across the screen
The resolution does not decrease with the age of the monitor as is the case CRTs.
The disadvantage is the cost although this is reducing rapidly.
An LCD monitor designed for connection to a PC does not usually have the required analogue inputs so check carefully before choosing this type of display